Less Boilerplate in Cljs Async Tests

I can mostly avoid async tests for my re-frame cljs apps. Even integration-style tests that use enzyme or react-testing-library can be made synchronous (if using Re-frame), by using day8.re-frame.test/run-test-sync and faking server responses with synchronous promises. This is nice because they’re easier to understand and debug. Sometimes though, async is necessary.

The Clojurescript site describes how to do async tests using the cljs.test/async macro and Re-frame has a nice run-test-async wrapper around that.

If you are using cljs.test/async you have to make sure your test code calls the done function in every case, including on errors, timeout etc. So to remove some boilerplate, here’s a new utility which provides a macro like cljs.test/async, but which on timeout or uncaught failure (exception or failed promise), will fail the test, calling the done function for you.

Here’s how you’d use it:

(ns myns.ns
  (:require [clojure.test :refer [is deftest]]
            [widdindustries.timeout-test :refer [async-timeout async-timeout-at]]))

(deftest my-test
  (async-timeout done 
     ;; do some stuff that will call `done` when it succeeds.
     ;; lib expects any async body will result in a promise
   ))

If you have any feedback please comment or raise an issue.

Henry

Written on September 4, 2019